At the title screen, press Select, Down, R2, L1, R1, L2. All features, including alternate costumes, outro FMV sequences, behind the scenes movie pictures, the Pool Party, and Psylocke, Juggernaut, Spider-Man, and Professor X will be unlocked. To use Spider-Man, highlight Cyclops and hold L1 at the character selection screen. To use Professor X, highlight Magneto and hold L1 at the character selection screen.

Play as Psylocke

Successfully complete the game with Wolverine in arcade mode to unlock Psylocke.

Play as Juggernaut

Successfully complete the game using all default characters and Psylocke in arcade mode to unlock Juggernaut.

Play as Professor Xavier

Successfully complete the game with Juggernaut. Then, highlight Magneto and hold L1 at the character selection screen.

Play as Spider-Man

Fight in arcade mode until you face Spider-Man. Defeat him and finish arcade mode. Then, highlight Cyclops and hold L1 at the character selection screen.